title: Hypoxia down-regulates sFlt-1 (sVEGFR-1) expression in human microvascular endothelial cells by a mechanism involving mRNA alternative processing.
abstract: sFlt-1 (soluble Flt-1) potently inhibits angiogenesis by binding extracellularly to VEGF (vascular endothelial growth factor). In the present paper, we report that hypoxia down-regulates sFlt-1 expression in HMVECs (human microvascular endothelial cells), a constituent of microvessels where angiogenesis occurs. Hypoxia (5-1% O₂) increased VEGF expression in HMVECs. In contrast, the levels of sFlt-1 mRNA and protein in HMVECs decreased significantly as the O₂ concentration fell, whereas mFlt-1 (membrane-bound Flt-1) mRNA and protein remained unchanged. This suggested that hypoxia selectively regulates alternative 3'-end processing of sFlt-1 pre-mRNA. We have also demonstrated that sFlt-1 overexpression in lentiviral-construct-infected HMVECs counteracted VEGF-induced endothelial cell growth. We next identified cis-elements involved in sFlt-1 mRNA processing in HMVECs using a human Flt-1 minigene and found that two non-contiguous AUUAAA sequences function as the poly(A) signal. Furthermore, we identified a cis-element in intron 13 that regulates sFlt-1 mRNA processing. Mutagenesis of the U-rich region in intron 13 caused a significant decrease in the soluble-form/membrane-form RNA ratio in the minigene-transfected HMVECs. These results suggest that decreased sFlt-1 expression due to hypoxia contributes to hypoxia-induced angiogenesis and reveals a novel mechanism regulating angiogenesis by alternative mRNA 3'-end processing.
authors.affiliation: Department of Biochemistry, Kanazawa Medical University School of Medicine, 1-1 Daigaku, Uchinada, Kahoku-gun, Ishikawa 920-0293, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ikeda
authors.forename: Li
authors.initials: L
authors.lastname: Sun
authors.forename: Naoki
authors.initials: N
authors.lastname: Tsuruoka
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Ishigaki
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yoshitomi
authors.forename: Yoshino
authors.initials: Y
authors.lastname: Yoshitake
authors.forename: Hideto
authors.initials: H
authors.lastname: Yonekura
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D001483:Base Sequence; D015687:Cell Hypoxia / Q000235:genetics; D002478:Cells, Cultured; D015536:Down-Regulation / Q000235:genetics*; D042783:Endothelial Cells / Q000502:physiology*; D006801:Humans; D008833:Microcirculation / Q000235:genetics*; D008969:Molecular Sequence Data; D026721:RNA 3' End Processing / Q000235:genetics*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics
chemical_list: D012333:RNA, Messenger; C501162:FLT1 protein, human; D040281:Vascular Endothelial Growth Factor Receptor-1